There is a vehicle lighting device including a socket and a light emitting module which is provided on one end side of the socket. The light-emitting module includes a substrate provided with a wiring pattern and a light-emitting diode (LED) electrically connected to the wiring pattern.
When a voltage is applied to the vehicle lighting device (light-emitting diode), the vehicle lighting device is turned on. When the voltage is applied to the light-emitting diode, a current flows through the light-emitting diode to generate heat, and a temperature of the light-emitting diode rises. In the case of the vehicle lighting device provided in automobiles, the voltage applied to the vehicle lighting device (light-emitting diode) fluctuates. Therefore, the temperature of the light-emitting diode becomes too high, and the light-emitting diode may be broken or the lifetime of the light-emitting diode may be shortened.
Therefore, a technique is proposed in which a resistor is connected in parallel with a circuit in which the resistor and a positive temperature coefficient thermistor are connected in series; and a current flows only in the resistor connected in parallel by shutting off the positive temperature coefficient thermistor in the case of an overvoltage.
However, in this case, the current flowing through the light-emitting diode abruptly changes when the thermistor shuts off, and thus the total light flux may suddenly fluctuate.
Accordingly, it is necessary to develop a technique in which a current can be prevented from flowing in the light-emitting element such as the light-emitting diode and sudden fluctuation of the total light flux can be prevented even when the voltage applied to the vehicle lighting device increases.